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The Biosphere: An Integral Part of the Planet and its Climate

This view of Earth highlights biological activity - specifically, the amount of photosynthesis happening. Higher chlorophyll concentrations in the ocean are indicated with green, yellow, and red colors. The amount of vegitation on land is indicated with incresingly deep shades of green.
Click on image for full size

SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE

Traditionally, Earth science classes and textbooks have focused on the non-living parts of the Earth (rocks and minerals, oceans, freshwater, ice, and the atmosphere). With the exception of living things that were fossilized long ago, life may not get much, if any, mention, even through it has an enormous impact on the planet. However, recently the impact of all the living things on our planet, known collectively as the biosphere, has garnered great attention as the biosphere’s connection to global climate has become increasingly apparent and critical.

In explanation of why the science of Earth’s climate had historically been neglected, scientist James Lovelock faulted the disconnect between the way living components of Earth are studied and the way non-living components of Earth are studied - that biologists, “failed to see that living things were tightly coupled to their material environment and that evolution concerns the whole Earth system with living organisms an integral part of it.”

While the term “biosphere” was first
coined over eighty years ago by Russian scientist Vladimir I. Vernadsky, thorough
study of the biosphere’s interactions with the rest of the planet has happened
mainly in the past few decades, since awareness of Earth as a system has grown
in the scientific community. For hundreds of years people have recognized some
of the connections between living things and climate, cutting down the trees
of a forest can change the temperature of the immediate area for example,
however the complex interrelationships between the biological and physical
parts of the Earth system were not well understood until Charles Keeling began
making detailed measurements of the amounts of carbon dioxide in the atmosphere
over time.

Since 1958 scientist Charles Keeling and others have measured the amount of carbon dioxide in the atmosphere in Hawaii. The yearly fluctuations in carbon dioxide are due to seasonal plant growth, while the overall rise in carbon dioxide over many years is due to a combination of fossil fuel burning, deforestation, and cement production.
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Windows to the Universe, based on data from UCSD and NOAA

In the 1960s, the connection
between rising atmospheric carbon
dioxide and global warming was
becoming clear and scientists began actively exploring the details of how carbon
got into and out of the atmosphere via, largely, biological processes. Dr.
Charles Keeling began making his now-famous measurements of carbon dioxide
in the atmosphere in 1958 from the top of Mauna Loa in Hawaii. Before Keeling
began taking measurements, we didn't know was
that the collective efforts of all the land plants in the Northern Hemisphere
as they wake up from their winter slumber and start to photosynthesize affects
the atmosphere worldwide. In just a short amount of time, a fraction of a
year, plants change the world. That is, before they once again drop their
leaves and head back into dormancy. When it is spring and summer in the Northern
Hemisphere, more plants are around to photosynthesize and extract carbon
from the atmosphere, the amount of carbon dioxide decreases by about 3%.
When it is autumn and winter in the Northern Hemisphere, there are fewer
plants doing photosynthesis, so more carbon dioxide in the atmosphere. This
is a natural fluctuation.

Keeling's data tell another story too.
At the close of each year, the carbon dioxide levels are a bit higher than
they were the year before. The yearly wobbles caused by plant photosynthesis
look like they are heading uphill on the graph because of an increase
in carbon dioxide over several decades. These data were the first concrete
evidence that the amount of carbon dioxide has been increasing. This overall
rise in the amount of carbon dioxide in the atmosphere is due to human impacts
on the planet - mainly burning fossil fuels. The graph of Keeling's carbon
dioxide data became known as the "Keeling
Curve" and continues to serve as an illustration of the impact of the
biosphere on the atmosphere, and the consequences in terms of global warming.

The Gaia Hypothesis, developed by James Lovelock in
the 1970s, emphasized the importance of the biosphere on the regulation of
Earth’s
climate. Lovelock’s scientific research focused on how the Earth’s atmosphere
was affected by the biosphere. The main tenet of the Gaia Hypothesis is that
our planet is analogous to a single cell – everything it has or could need is contained
within the cell aside from energy that comes in from the Sun.
Taken too literally, this may sound completely absurd.However, the
general idea of Earth as a contained system is now widely accepted. This idea
of Lovelock’s dovetails
well with the idea, formulated about a decade later in the 1980s, of Earth
system science, that the parts of our planet are interconnected in a multitude
of ways.

Today,
interdisciplinary research combining biochemistry, geochemistry, biology, hydrology,
and atmospheric science helps us to better understand the biosphere’s role
in the Earth system and, in particular, how biogeochemical
cycles affect the Earth system. This understanding of the biosphere forms
part of the framework utilized by supercomputer models, which describe and
predict the Earth’s climate.

In this week of the course we will examine the Earth’s biosphere and how changes in the cycling of carbon and nitrogen between the living and non-living parts of the Earth system are causing changes in climate. We will also find out how Earth’s warming climate is affecting aspects of the biosphere. This week’s classroom activity will put your students into the nitrogen cycle, and an online interactive will allows them to surf through the carbon cycle. We will also discuss carbon credits, a topic of current debate among scientists, social scientists, and policy makers.

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